Are you intrigued by how spring tides work ? This is the phenomenon that causes the shoreline to sometimes move closer to the beach and at other times farther away from the shoreline. In this article, we'll provide all the information you need about them: their causes, types, effects, and more.
Spring tides
Tides are a marvel that causes the beach to sometimes fill with more water, raising its level, and at other times, making it appear to have less volume or water level. Essentially, they are cyclical movements of large bodies of water due to the gravitational pull exerted by the moon and the sun on the Earth. When discussing tides, they are usually divided into spring tides and neap tides.
Formation of Spring Tides
The Sun and the Moon practice a gravity action on our planet, which produces cyclic displacements of these bodies of water. Sometimes, the attractive force of gravity acts together with the inertia produced by the rotation of the earth and in these cases the tides are more prominent. Because the moon is closer to Earth, the effect it has on bodies of water is greater than that of the sun.
Our planet makes a return on itself every 24 hours, it is the so-called rotation movement. If we could see it from space, we might be able to see the Earth and Moon align once a day. This singularity could make us think that there are tidal cycles of one for every 24 hours. But they actually occur in cycles that last about 12 hours.
This happens because, when the moon is directly above an ocean, it exerts its power of attraction on the waters and they rise. This is because our planet and the moon form a regime that moves around a center of rotation. When this happens, on the opposite side of the Earth, a rotational movement is verified that produces a centrifugal force.
This centrifugal force is capable of causing the waters to rise, producing what is known as high tide. Now, what happens to the faces of our planet that are opposite the moon and that are not affected by the pull of gravity will experience low tide.
To appreciate the true cycle of spring tides , one must imagine that at the same time that our planet rotates on its own axis during the rotation movement, the Moon's movements are also occurring as it revolves around the Earth in a translational movement, managing to advance approximately 12° daily and requiring 29 days, 12 hours, 44 minutes and 3 seconds to complete its orbit.
This movement of translation of the moon, causes that from any place on earth it takes us a little more than 24 hours to find ourselves aligned again in front of the moon. In fact, specifically it takes 24 hours, 50 minutes and 28 seconds. That is what is called a lunar day and that is the time by which the cycles of the tides are governed.
From what we have just explained, in theory, the tide span is about 12 hours, 25 minutes and 14 seconds between high tide and high tide; and 6 hours, 12 minutes and 37 seconds between high tide and low tide. With this, what we want to indicate is that, in theory, since mathematics is usually not exact regarding these matters, it is that each type of tide is 12 hours.
The spring tide is not always the same, since there are several factors that influence its capacity. Although common knowledge indicates that the cycles between low tide and high tide last about 6 hours, in context this is not really the case. Our planet is not exclusively made up of water. It is known that there are continents, coastal orography, depth silhouettes, storms, ocean currents and winds that have an active influence on the tides.
As we have already tried to explain, spring tides occur in relation to the position of the moon and the sun. When these celestial bodies are aligned with the Earth, the gravitational pull is strongest. This usually happens when the moon is in its full or new moon phase. These alignments result in higher tides, which are then called spring tides.
On the other hand, when the Earth, the sun and the moon are placed at a right angle, the attractive force of gravity is much less. When the tides occur at these times, they are known as neap tides. These neap tides occur when the moon is in the first quarter phase and in the last quarter phase.
Definitions related to Spring Tides
With the aim of clarifying the meaning of many terms used in relation to spring tides , in this section of the article we propose to explain the meaning of several of them, which may be useful to the reader:
- High tide or high tide: occurs in the period in which the sea reaches its maximum level within the tidal cycle.
- Low tide or low tide: is the one that occurs when the water level of the tide period reaches the minimum.
- high tide time: it is the moment in which the high tide occurs or, what is the same, the moment of greatest height of the sea level in a certain place.
- Low tide time: it is the moment in which the low tide is verified, or, which is the same as saying that it is the instant of lowest height of the sea level in a certain place.
- Emptying: This is the period between high tide and low tide.
- Growing: is the period between low tide and high tide
Types of Spring Tides
There are multiple variables that affect and exert their influence on the tides and, due to these variables, there are several types of tides:
Normal Spring Tides
They are also called syzygies. These are the spring tides that are the most usual, this means, that they are the ones that appear at the moments in which the sun, the moon and the Earth are aligned. It is at this moment that the attractive force of gravity is at its maximum. And as we have said in a previous section of this article, they are verified when the moon is in full moon phase and in new moon phase.
Equinoctial Spring Tides
This type of spring tides is verified when another factor that determines the behavior of the water masses is added. These occur when the stars align on dates that are very close to the spring or fall equinoxes. Another fact to take into account is that they occur when the Sun is positioned absolutely on the plane of the terrestrial equator. When this happens, the spring tides have greater intensity.
Perigee Equinoctial Spring Tides
This kind of spring tides occur when all the variables that we have mentioned above come together, but, additionally, the moon is in its perigee phase. It is when all these variables come together, when high tides are greater than at any other time, and this is due to the close proximity between the Earth and the moon when this occurs.
In addition, the moon, the sun and the Earth being aligned, the force of gravity is increased. At the times when this type of spring tide occurs, it is when the coastal areas are most affected and when the volume of water on the beaches is reduced by more than half.
Why are there no tides in the Mediterranean Sea?
The statement is not correct, because if there are spring tides in the Mediterranean Sea, what happens is that in that sea they are practically imperceptible. This is because the Mediterranean is a sea that is almost completely closed. Its only freshwater inlet is through the Strait of Gibraltar.
However, the Strait of Gibraltar is a very small waterway and is not capable of attracting a large volume of liters of water from the Atlantic Ocean. For that reason, this volume of water is trapped in the strait. These peculiarities cause the Strait of Gibraltar to operate like a kind of faucet that closes. In addition, if there is the possibility that a robust inflow current is born but is unable to reach the Mediterranean Sea.
And all this occurs at very long time intervals, so it can be said that there is not enough time for the Mediterranean Sea to experience the effects of the tides coming from the Atlantic Ocean.
However, the effects of the tides can be observed a little in certain special and more select seasons, but it will never be a strong spring tide. During the time of the low water, the opposite occurs and, paradoxically, from the Strait of Gibraltar there is a strong outflow current towards the Atlantic Sea.
Another factor to consider is that the Mediterranean Sea is relatively small, so the gravitational pull of the moon is weaker. The Mediterranean's topography is characterized by numerous headlands, points, and coastlines, and spring tides are only noticeable in differences of a few centimeters.
How was the origin of the tides explained in ancient times?
It might surprise you, but the understanding of spring tides, and the elements that produce them, is of recent date. This has historically been the case because, as we just explained in a previous section of this article, the tides in the Mediterranean Sea, which was the cradle of Western civilization, are almost imperceptible, so they were not considered very important.
On the other hand, in order to understand the way in which spring tides work, it is also necessary to understand the forces that are generated from the cosmos and the way in which the waters are distributed in Seas and oceans, something that was not possible to understand until not long ago. In fact, in some cultures, the behavior of spring tides was thought to be the way the heart of our planet beat.
Why is it convenient to know the tide schedule?
If you are going to carry out any activity related to the sea, such as diving, you need to know the tide schedule, because in some places we run the risk of being trapped by a high tide and leaving us exposed to dangerous situations.
This is precisely what happened to Julius Caesar, who when he went to conquer Britain, was caught by an incoming spring tide and was trapped with all his armies at the mouth of the River Thames, in the English Channel.
In the case of a diver, an ebb is capable of dragging him out to sea, without being able to return to shore. That is the reason why it is recommended to dive in periods of low spring tide, and you have to get out of the water just before the tide rises. It is advisable to always consult the spring tide tables before carrying out this type of activity or use a calculation application as a safety measure.
What are the highest known spring tides?
The highest known occur in the Atlantic Sea, in the Bay of Fundy, off the coast of Canada. It has been possible to measure that the water level has fluctuated up to 19 meters between high tide and low tide. Also in the area of French Brittany, in the area of Mount Saint Michel, an oscillation of 16 meters has been measured.
